1. Field of the Invention
The present invention relates to an antistatic agent for polyacetal resins exhibiting excellent antistatic effect and to a polyacetal resin composition using the above agent. More specifically, the invention relates to an antistatic agent which imparts stable antistatic effect to the polyacetal resins and is little dependent upon the environment, without impairing mechanical properties, thermal properties, moldability and machinability.
2. Description of the Prior Art
Owing to their excellent mechanical properties, thermal properties, long-lasting properties, abrasion properties, moldability and machinability, the polyacetal resins have been used as engineering plastic materials in a broad field of applications such as automobiles, electric and electronic appliances. Like many other plastic materials, however, the polyacetal resins have high surface resistivities causing troubles that stem from the electrification such as electrostatic noise, surface fouling, and adhesion of matters, depending upon the applications. In order to eliminate such troubles, a variety of antistatic agents have heretofore been used.
Such antistatic agents are effective even for the polyacetal. However, the ionic substances, such as anionic and cationic antistatic agents, and a mixture of a polyethylene oxide (PEO) and an alkali metal salt (e.g., Japanese Laid-Open Patent Publication No. 139266/87), are not desirable since they cause the polyacetal to be discolored and to lose the thermal stability. Nonionic antistatic agents have been proposed giving little adverse effects, which, however, exhibits generally small antistatic effect and must be added in large amounts if it is attempted to decrease the electrification properties down to the practicable level.
However, addition of the antistatic agents in large amounts generally causes the molded articles to lose their mechanical properties, moldability and machinability and, particularly, causes much bleeding on the surfaces of the molded articles to deteriorate the appearance. In general applications, furthermore, the antistatic agents have problems in maintaining antistatic effect and stability, such as losing the antistatic effect when the molded articles are washed with a solvent or are preserved in a low-humidity environment.